Observability Tasks: Building Observability Documentation（可观测性文档建设）

- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.

## Describe the proposal

En: Here we need to sort out a complete observability document. For specific content, please refer to the observability of SpringBoot3, such as the link:
[https://docs.spring.io/spring-boot/docs/current/reference/html/actuator.html#actuator.enabling](https://docs.spring.io/spring-boot/docs/current/reference/html/actuator.html#actuator.enabling)
- Observability documentation: output background and architecture documentation
- Getting Started Documentation: Output Getting Started Access Documentation
- Getting Started Example and Parsing Documentation: Output Example
- Principle analysis: output principle documents
- Observability practice: Troubleshooting case analysis Collect common Dubbo exceptions Output fault analysis classification and documents

这里需要梳理出一个完整的可观测性文档，具体内容可以参考SpringBoot3的可观测性，如链接：
[https://docs.spring.io/spring-boot/docs/current/reference/html/actuator.html#actuator.enabling](https://docs.spring.io/spring-boot/docs/current/reference/html/actuator.html#actuator.enabling)
- 可观测性说明文档：产出背景与架构文档
- 入门使用文档： 产出入门接入文档
- 入门示例与解析文档： 产出例子
- 原理解析： 产出原理文档
- 可观测性实战： 故障排查案例分析 收集常见Dubbo异常 产出故障分析分类与文档

Review the issue proposal alongside the linked Spring Boot Actuator observability documentation. Define the documentation structure for background and architecture, getting started, examples, principles, and troubleshooting cases. Done means these five observability areas are documented for Dubbo, but the issue does not name repository files or tests to run.

Written by the indexing model from the issue text.